KR20120016240A - Adaptive buffer status reporting - Google Patents

Abstract

The present invention relates to a method for communicating from a first station to a second station in a network, the first station comprising at least one buffer memory for storing data packets to be transmitted, the method comprising (a) first The first station estimating the state of the at least one buffer memory, (b) the first station transmitting at least one buffer state packet indicative of the buffer memory state, the method comprising (c) data traffic characteristics; Adapting the value of the first parameter of the buffer status packets based on the.

Description

Adaptive Buffer Status Reporting {ADAPTIVE BUFFER STATUS REPORTING}

The present invention relates to a method for communicating in a communication network. In particular, the present invention relates to a method for communicating from a first station and a second station. The invention also relates to radio stations that can implement such a method.

The present invention relates, for example, to all wireless communication networks and, in the examples of the following specification, to mobile telecommunication networks such as UMTS or UMTS LTE.

In a cellular network, each cell includes a base station or a primary wireless station, such as a Node B or eNB, that communicates with mobile stations or a plurality of secondary stations, such as user equipment. In order to be able to transmit data to the primary station on some uplink channels, the secondary station typically has allocated resources (eg, time slots, frequency subcarriers, and / or codes). Must have

Many communication systems operate using a centralized scheduler that assigns transmission resources to different nodes. A typical example is the uplink of UMTS Long Term Evolution (LTE), where uplink transmissions from different secondary stations are scheduled at time and frequency by the primary station. The primary station sends a " scheduling grant " message to the secondary station, and typically indicates about 3 ms of specific time-frequency resources for the transmission of the secondary station after transmission of the grant message. The grant message also typically specifies transmission parameters such as data rate and / or power to be used for secondary station transmission.

In order for the primary station to issue an appropriate grant, it is necessary to have enough information about the amount and type of data awaiting transmission in the buffer of each secondary station.

Therefore, in LTE, several types of buffer status report (BSR) messages are defined that can be sent from the secondary station to the primary station when certain triggers occur. The current version of 3GPP TS36.321 is incorporated by reference.

The buffer status reporting procedure is used to provide the serving primary station with information about the amount of data in the uplink buffers of the secondary station. Depending on the events, two kinds of buffer status reports are used. The short buffer status report (BSR) contains the identity of a single group of logical channels, with a six-bit indicator of the amount of data currently residing in the secondary station buffer waiting for transmission and corresponding to the group of logical channels. do. The long BSR includes four contiguous short BSRs, each corresponding to a group of different logical channels.

The problem with the prescribed BSR procedure is that the secondary station is only allowed to transmit BSR if the secondary station has authorized resources to transmit. If the secondary station does not have authorized resources to send new data to the secondary station's buffer and send data or BSR indicating that it has data waiting to be sent, the secondary station is granted permission. It must either wait until received or transmit a more simplified version of the BSR that can be sent using some specially-designated resources that can be used without designated authorized resources. A more simplified version of this BSR is known as a "scheduling request" and typically contains only a single bit indicating that the data is in a buffer. SR is known to include a small number of bits, but this provides greater functionality. In response to receiving the SR, the primary station transmits a BSR after sending an authorization to allocate an appropriate amount of transmission resources to the secondary station, or enables the secondary station to transmit some data other than the BSR. may transmit a grant that allocates a larger amount of transmission resources to enalbe; In the latter case, however, there is typically no means to determine the proper size of the allocation that the primary station will make, unless the SR contains one or more bits.

As a result, it is not possible to have a reasonable amount of information in known implementations for notifying the primary station of the status of the buffers of the secondary station. In fact, when the activity of the secondary station is low, BSRs transmitted regularly are more than sufficient, and thus do not use resources in an efficient manner. Conversely, if the activity of the secondary station is large, the BSR may not provide enough information about the actual state of the buffers of the secondary station.

It is an object of the present invention to propose an improved method of alleviating the above problems for communication in a network.

Another object of the present invention is to propose a method for efficiently utilizing resources by communicating the state of buffers of a mobile station in an efficient manner.

Another object of the present invention is to propose a method for signaling the state of buffer memories in a manner adapted to the situation of a secondary station.

According to a first aspect of the invention, a method for communicating from a first station to a second station in a network is proposed, wherein the first station comprises at least one buffer memory for storing data packets to be transmitted, wherein Way

(a) the first station estimating the state of the at least one buffer memory,

(b) the first station transmitting at least one buffer status packet indicative of the buffer memory status, the method comprising (c) adapting the value of the first parameter of the buffer status packets based on the data traffic characteristic; It further comprises a step.

In exemplary embodiments, the first station is a secondary station (or user equipment or mobile station) and the second station is a primary station (or eNodeB, base station).

According to another aspect of the invention there is provided a wireless station comprising means for communicating in a network having at least additional stations, the first station comprising at least one buffer memory, at least one buffer memory for storing data packets to be transmitted. Buffer control means for estimating a state of the data, transmitting means for transmitting at least one buffer state packet indicative of a buffer memory state, wherein the buffer control means includes a value of a first parameter of the buffer state packets based on a data traffic characteristic. A wireless station is proposed that is arranged to adjust.

Due to these features, a wireless station, such as a secondary station, can adapt the amount of information sent to a second station, such as a primary station, depending on the situation of the secondary station or the overall occupancy of the network. Therefore, this makes it possible to effectively use the resources granted to the secondary station to signal the status of the buffer memory.

Moreover, in a variant of the invention in which secondary stations communicate on a plurality of logical channels, the buffer memories may comprise a plurality of logical channel buffers, the status of the buffer memories being independently signaled to each other, step (c) It should be noted that the adaptation of is done in one or more logical channel status reports. Therefore, logical channel status reports dedicated to a less active logical channel may be signaled less frequently or with a lower accuracy, so that logical channel status reports dedicated to a more active logical channel are more frequent or with higher accuracy (e.g., May be signaled).

These or other aspects of the invention will be apparent from and elucidated with reference to the embodiments described below.

1 is a block diagram of a network in which the present invention is implemented.
2A and 2B are time charts illustrating the adaptation of signaling according to the first embodiment.
3A, 3B, and 3C are time charts showing a modification of the first embodiment.

The invention will now be described in more detail by way of example with reference to the accompanying drawings.

The present invention relates to a communication network having a primary station and a plurality of secondary stations in communication with the primary station. Such a network is shown in FIG.

Referring to FIG. 1, a wireless communication system according to the present invention includes a primary wireless station (BS) 100 and a plurality of secondary wireless stations (MS) 110. The primary station 100 is a microcontroller (μC) 102, transceiver means (Tx / Rx) 104 connected to the antenna means 106, power control means (PC) for changing the transmitted power level ( 107, and connection means 108 for connection to a PSTN or other suitable network. Each secondary station 110 has a microcontroller (μC) 112, a transceiver means (Tx / Rx) 114 connected to the antenna means 116, and a power control means for changing the transmitted power level ( PC) 118. Communication from the primary station 110 to the mobile station 110 occurs in the downlink channel, while communication from the secondary station 110 to the primary station 100 occurs in the uplink channel.

In the centrally controlled wireless packet-data networks such as the network of FIG. 1, the secondary stations 110 (or user equipment, or UE in UMTS LTE) differ from the primary station 100 (or eNB in UMTS LTE terminology). What is needed is a mechanism to enable effective prioritization of the allocation of uplink transmission resources between the < RTI ID = 0.0 > Each secondary station typically has data queued in buffers until it can transmit; There may be buffers for multiple different streams, or logical channels (LCs), each having different quality of service (QoS) requirements. The primary station needs information to enable to determine which secondary station should be transmitted and at what speed. To aid this process and reduce overhead, group LCs into LC groups (LCGs) and send an indication of buffered data for different LCGs (ie, buffer status reports (BSRs)). It is possible.

As mentioned above, in such a system, for example UMTS LTE, the number of bits allocated to BSRs is typically predetermined and the same for all LCGs. Moreover, complete buffer status knowledge at the primary station 100 is often assumed; That is, the primary station has very finely quantized information about the number of bytes in the buffers of the secondary station. Some simulations indicate that it may be more useful to send more subtle buffer status updates, especially for real-time functions, than farther detailed reports. As a result, the fixed buffer status report (BSR) length, which is designed to provide accurate buffer status information, has the following disadvantages:

1. This results in significant overhead, which would not be reasonable given that in some cases the same or similar performance can be achieved with fewer bits allocated to the BSR.

2. This prevents BSRs for multiple LCGs from being fed back to the primary station if only a fraction of the total number of bits required is available; In such cases, current systems will provide a full BSR only to the LCG with the highest priority. (An example of such a case would be the transmission, with the result needed to fill some padding permitted resources. Occurs when the amount of data to be made is smaller than the allowed transmission resources; in that case some or all of the padding bits may be replaced by BSR signaling, but the number of such padding bits available to be replaced is It may not be enough to be transmitted for all LCGs.)

The present invention is based on the recognition that BSRs need to be adapted to the situation of data traffic of an entire network, a particular secondary station, and / or a group of logical channels corresponding to a BSR. According to a first embodiment of the invention, the proposed solution is to enable the frequency and / or coarseness of the configurable BSRs. As a result, according to the first embodiment of the present invention, the present invention estimates the level of BSR roughness suitable for the secondary station itself or a specific scenario within the primary station, and then roughness of BSR signaling according to the estimated value. In order to adapt the circuit. An example of this embodiment is shown in FIG. 2A. According to this example, the secondary station in the first phase of operation 200 periodically transmits one BSR 201 dedicated to at least one logical channel. After estimating the data traffic characteristics that cause the secondary station to enter the second phase 300, such as more stringent QoS requirements for this logical channel, or higher activity, the secondary station can more accurately determine the BSRs 301. For example, transmit with more bits. As a result, at a given time, the amount of data dedicated to this logical channel and transmitted is greater in the second phase 300 than in the first phase 200. Therefore, BSRs are adapted over time.

According to a variant of the first embodiment shown in FIG. 2B, the BSRs 302 in the second phase 300 are transmitted more frequently than the BSRs 202 in the first phase 200. The size of the BSRs does not change. As a result, as in the first example of FIG. 2B, over time, the amount of data dedicated and transmitted to this logical channel is greater in the second phase 300 than in the first phase 200. Therefore, BSRs adapt over time.

It should be noted that these two examples may be combined where, for example, BSRs are transmitted more often, and for example with lower accuracy.

According to the first embodiment, the second phase is entered after estimation of the characteristics of specific traffic profiles. Possible candidates are:

a. Traffic strength, which can be defined by the average number of new arrivals into the system;

b. Total system QoS requirements, such as the total number of satisfied users.

c. Type of traffic (for example, VoIP or video or file transfer).

d. The amount of data buffered for one or more traffic flows.

This estimation can be done by the primary station 100 and can be done for each logical channel group. The primary station can then transmit the estimated characteristic value, which the secondary station explicitly signals from this value for the appropriate BSR coarseness (by adapting the accuracy or frequency of the BSR), or even for each LCG. Infers the BSR coarseness. This value may be different for different LCGs.

Prior to explicitly signaling BSR coarseness for each LCG individually, grouping of LCs into LCGs may be performed by the network (eg, based on similarity between BSR levels sufficient for satisfactory performance). . In a variant of the invention, the BSR coarseness is estimated based on the number of available padding bits or taking into account the actual scheduling algorithm used.

In a second embodiment of the present invention, a table of satisfaction levels of BSR coarseness and range of varying traffic loads for a given QoS can be produced for VoIP traffic. Depending on the actual traffic volume in the system, known to the primary station, the secondary station can actively adapt BSR coarseness based on traffic load information from the primary station.

Another example is the case of padding BSR in UMTS Rel-8 (LTE). If there is more than one LCG with buffered data and there are not enough bits to transmit a long BSR, determine which LCG causes their BSRs to be transmitted, not just the highest priority BSR among the LCGs. The mechanism is devised in accordance with the present invention. This decision is:

1. Priorities: 2, 3 or 4 LCGs with the highest priority are selected, not just the LCG with the highest priority;

2. Buffer level fills: In addition to priorities, a threshold that, when exceeded, indicates that the LCG is entitled to send its own BSR, or adapts the granularity of the BSR. Can be introduced.

3. It may be based on a head-of-line delay (ie, the length of time that the oldest packet is in the buffer).

In addition, formats are proposed below that enable two, three, and four coarse BSRs to be combined into octets. The BSR format being transmitted may be indicated by an LCID value, as in the first version of LTE. New LCID values will need to be reserved for these three formats in FIGS. 3A-3C.

In FIG. 3A, if four LCGs are signaled to the primary station in one BSR: In this case, similar to the long BSR, there is no need to indicate the IDs of the LCGs, and providing the corresponding BSRs in the correct order. (Because only four LCGs are defined in LTE; in general, this format applies to the transmission of BSR information for all configured LCGs). In an embodiment where 8 bits are available, this means having 2 bits for each of the 4 LCGs, as shown in FIG. 3A.

In FIG. 3B, if three LCGs are signaled to the primary station in one BSR: If three 2-bit IDs must be transmitted, only 8-6 = 2 bits will remain for the three BSRs in LTE. An alternative is proposed below in which the three 2-bit BSRs are reported in the correct order after reporting the ID of the LCG for which the BSR is not being reported (LCG # 2 in this case).

In FIG. 3C, only two LCGs are signaled with one BSR, where the IDs of the two logical channel groups are signaled with the value of the buffer state of this LCG. For 8-bit BSR, 2 bits are used for the ID and 2 bits are used for the value of the buffer state of this LCG.

In another embodiment, the BSR length is set according to the traffic class. For example, for a LCG that includes at least one data flow with a secondary station having a multi-level satisfaction criterion (eg, FTP download, where the degree of user satisfaction typically increases with decreasing transmission delay). The long station can transmit long BSRs, while the secondary station depends on a two-state satisfaction criterion (e.g. VoIP service, where the user is typically satisfied or otherwise a percentage of packets successfully delivered for a fixed time period). Shorter BSR may be transmitted for an LCG that includes only data flows.

Another embodiment is a case where the frequency at which the BSR is transmitted is configured in advance. The secondary station can in this case adjust the length of the BSR to achieve the required QoS in a manner according to the preconfigured frequency.

In cases where estimation of the appropriate BSR length is performed at the base station, the base station signals the result of the estimation to the UE. Therefore, in a typical embodiment, the UE may receive a list of logical channels, logical channel groups or priorities, with corresponding BSR lengths corresponding to each.

In a variant of the invention, the primary station is a mobile terminal, such as user equipment, and the primary station is a base station, such as an eNodeB.

The present invention is applicable to mobile telecommunication systems such as UMTS LTE and UMTS LTE Advanced, and may also be applicable to any communication system that allocates resources that are dynamically or at least semi-permanently done in some variations. .

In this specification and claims, "a" or "an" before an element of a word does not exclude the presence of a plurality of such elements. Moreover, the word "comprising" does not exclude the presence of other elements and steps than those described.

The inclusion of reference signs in parentheses in the claims is intended to aid the understanding and is not intended to be limiting.

From reading this specification, other modifications will be apparent to those skilled in the art. Such modifications may include other features that are already known in the art of wireless communication.

Claims (16)

A method for communicating from a first station to a second station in a network, the first station comprising at least one buffer memory for storing data packets to be transmitted:
(a) the first station estimating a state of the at least one buffer memory,
(b) the first station transmitting at least one buffer status packet indicative of a buffer memory status,
(c) adapting a value of the first parameter of the buffer status packets based on data traffic characteristics. 2. The method of claim 1, wherein the first parameter comprises an amount of information transmitted by the buffer status packets at a given time. A method according to claim 1 or 2, wherein the first parameter of step (c) comprises the size of the buffer status packets. 4. The method of any one of claims 1 to 3, wherein the first parameter of step (c) comprises a granularity of information contained in the buffer status packets. The method of any one of claims 1 to 4, wherein the first parameter of step (c) comprises the frequency of transmission of the buffer status packets. 6. The method of any of claims 1 to 5, wherein the data traffic characteristic is estimated by the second station, and the method further comprises the step of the second station signaling the data traffic characteristic to the first station. Further comprising, in step (c) the first station adapts the value of the first parameter of the buffer status packets based on a signaled data traffic characteristic. 7. The method of any one of claims 1 to 6, wherein the data traffic characteristic is estimated by the second station, and the method further comprises the step of the second station being connected to the first station in step (c). Signaling the value of the second parameter of the buffer status packets to be used by the method. 8. The method of claim 7, wherein step (c) includes the first station receiving the second parameter value, wherein the first station is further based on the received value of the second parameter. Adapting the first parameter of the apparatus. 9. The method of claim 8, wherein the first parameter of the buffer status packets is the same as the second parameter. 10. The method of any of claims 1 to 9, wherein the buffer memory includes a plurality of logical channel buffers, each logical channel buffer configured to store data packets dedicated to each logical channel or group of logical channels. Wherein the buffer status packets comprise at least one part dedicated to information about the status of one respective logical channel buffer, and in step (c), for each part, the first parameter is considered And the portion is adapted according to the logical channel or group of logical channels to which it relates. 12. The method of claim 10, further comprising grouping the logical channels into a group of logical channels according to having substantially the same first buffer status packet parameter value. 12. The method of claim 10 or 11, wherein step (c) further comprises selecting a subset of logical channel buffers, and transmitting a buffer status packet indicating the status of the selected logical channel buffers. Communication method. 13. The method of claim 12, wherein the subset size is signaled by the second station. 13. The method of claim 12, wherein the logical channel buffers are as follows: priority of the logical channel, head of line delay, logical channel buffer fill levels, or padding available within a data packet. and selected based on at least one of the number of bits. 15. The method according to any one of claims 1 to 14, wherein the data traffic characteristic is based on the following characteristics: traffic strength, QoS requirement, total number of satisfied users, type of traffic, one or more traffic flows or logical channels. And at least one of an amount of buffered data for the state, a state of the buffer memory, and a number of padding bits available in the data packet. 12. A wireless station comprising means for communicating in a network having at least additional stations, the first station comprising: at least one buffer memory for storing data packets to be transmitted, a buffer for estimating a state of the at least one buffer memory Control means, transmitting means for transmitting at least one buffer status packet indicative of the buffer memory status, wherein the buffer control means is arranged to adjust a value of a first parameter of the buffer status packets based on a data traffic characteristic. Being, a wireless station.

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